Fix implementation of VCVT.F64.
Add implementation of STRBT, STRHT, LDRBT, LDRSBT, PLI.
Add implementation of SSAX, SXTAB16, SHASX, SHSAX, SHSUB8, UASX, USAX, UQADD16, UQASX, UQSAX, UHASX, UHSAX, REVSH.